DE4300495B4 - Procedure for testing dental casting materials - Google Patents

Abstract

Method for testing dental casting materials, wherein during the melting of the dental casting material, time-dependent temperature values or temperature-related values of the dental casting material are measured, which form a measurement curve (11), and the solidus point (12) is determined on the basis of the measured time values and temperature values or temperature-related values and the Temperature value ( I ₁₀₎ or the temperature-related value (I ₁₀₎ and the value (t ₁₀₎ at the solidus point (12) of a reference curve (10) to the temperature value (I ₁₁₎ or the temperature-related value (I ₁₁₎ and the value (t ₁₁₎ at the solidus point (12) of the measurement curve (11) in relation to the formation of two ratio factors and the measured time values and temperature values or temperature-related values are multiplied by the associated ratio factor, whereby a standardized measurement curve (14) is created, which is compared with the set curve (10 ) is compared.

Description

The The invention relates to a method for testing dental casting materials.

to Manufacturing dental castings are usually made up of several elements composite materials (alloys) are used. critical for the quality the dental castings is the quantity ratio of the individual elements, especially the amount of alloy components. That's why they have to Dental casting materials are checked for their correct alloy.

It it is known that the temporal temperature curve during melting of the dental casting material the respective alloy allows because each alloy has a characteristic temperature-time profile. For this reason, the Dental casting materials based on the temperature-time course during melting. However, there has been an evaluation of the determined temperature-time profile the melt proved difficult because, on the one hand, the deviations different alloys are sometimes only very small and others themselves. the temperature-time curves depending on the particular Change the amount of dental casting material to be melted.

From the DE 27 42 576 C3 a device for measuring the carbon content of a sample of a steel or cast iron melt is known. The carbon content of the melt is determined using the cooling curve of a sample. In this case, a difference between successive temperature measurement values is formed and a comparison is made as to whether the currently determined temperature difference is larger or smaller than the previously determined temperature difference. The measurement of the carbon content known from this document does not allow any conclusions to be drawn about the respective alloy. In addition, the measurement based on the cooling curve of the sample is disadvantageous because the casting has then already taken place.

task The present invention is the testing of dental casting materials to simplify and reliably based on their temperature-time profile do.

to solution this object of the inventive method has the features of Claim 1 on. By normalizing the actual values determined time-temperature values, which always means values proportional to time and temperature, to at least one specific setpoint, in particular time-temperature setpoint (including time-target temperature-proportional values), quantity deviations of the dental casting materials to be melted. So pose the standardized time-temperature values decoupled F Actual values represent the test simplify considerably. As a result of what continues to take place according to the invention Comparison of the standardized actual time-temperature values with setpoints, in particular time-temperature setpoints, can be relatively small Determine alloy deviations, which ensures precise testing is.

It the determined time-temperature actual values are standardized a single (specific) time-temperature setpoint, namely a solidus point. This is the point where the solid dental casting material begins to liquefy. This point is characterized by the solidus temperature or a temperature proportional to the solidus and the associated time, that is, the point at which the solid dental casting material begins, to liquefy. This is a characteristic point that with relatively large Accuracy for every amount of dental casting material to be melted and every alloy is detectable.

The Solidus point of the test Alloy is on the solidus point of a given target alloy based. To do this, the conditions the times and the temperature values or the temperature proportional Relative values at the solidus points. Which is thereby resulting ratio factors (for the Time and the temperatures or values proportional to the temperature) to the rest time-temperature values of the alloy to be tested and thereby standardize. In this way arise for comparable Alloys of different quantities have corresponding time-temperature values.

The Comparison of the test items Alloying with the target alloy takes place in that temperature values or temperature-proportional values of the same times compared become. Are the deviations of the standardized time-temperature values the one to be checked Alloy within a specified, permissible limit value in relation to the respective Time-temperature setpoint of the specified alloy corresponds to the to be checked Alloy the specifications, so is fine. However, at least fall some of the standardized time-temperature values of the alloy to be tested from the allowable The scattering range of the given alloy is a sign for this, that the alloy to be tested does not meet the requirements.

According to a preferred method, the dental casting alloy is tested using Di agrammen. For this purpose, a comparison diagram with the specified (ideal) alloy is compared with a test diagram formed from the standardized time-temperature values of the alloy to be tested. In this way a visual control is possible.

to Facilitation of visual control in particular is after a Further development of the invention provided the comparison diagram to form two (upper and lower) curves, the upper and lower Show limit values of the time / temperature setpoints. The comparison with the test diagram then takes place in such a way that test chart in the area of the surface enclosed between the upper and lower curves Comparison diagram must lie if the one to be checked Alloy meets the requirements.

A Another special feature of the invention is that at least the (standardized) test diagram from one of the melting or pouring devices assigned printer is printed. This makes the test data practical in a casting record documented. At the same time the test diagram easily compare the comparison diagram, for example as a template the test diagram is placed. Alternatively, it is conceivable to use both the (standardized) test diagram as well as the related Comparison diagram (possibly with upper and lower limit value curves) print out together. Then the comparison can be done at any time without any problems be made. It can be traced at any time without requiring a (separate) comparison diagram must be available.

According to the invention, both time-related temperature values as well as time-related temperature proportional Values are used. If (especially in the claims) we are talking about "determined time / temperature values" this relates both to time-related temperature values and time-related temperature proportional values.

As it has proven to be particularly advantageous to use time-related temperature-proportional Use values to form the standardized test values, as these simply contactless can be determined by, for example, infrared radiation measuring devices. ever according to the distance to the melt, the transfer properties the corresponding sensors and the ambient temperature these are only qualitative values, but are always temperature-proportional and deliver meaningful comparative values through standardization.

preferred embodiments the invention are explained below with reference to the drawing. In the drawing shows:

1 a diagram with a target curve and a measurement curve from measured individual values,

2 the diagram according to the 1 with an additional standardized measurement curve shown in dashed lines, and

3 a comparison diagram of two (upper and lower) limit curves and the normalized measured curve shown again in dashed lines according to the 2 ,

At the to water of dental castings becomes a blank of the to be cast Material made of, for example, a titanium alloy is melted and subsequently in an appropriate mold cast. Crucial for the quality of the dental part to be cast is the composition of the cast alloy. According to the invention, this is therefore simple and meaningful Way to check and to document.

At the The method described below is used during the melting of the casting material, ie time-dependent, those on the surface of the first still solid casting material and later liquid casting material radiated heat measured. Infrared radiation values are preferably determined. These values are proportional to the instantaneous temperature of the cast material. The infrared radiation energy also increases with increasing temperature to. These measurement values obtained in this way can therefore are considered qualitatively as time-temperature values, which is why they are also called simply in the following.

First, time-dependent temperature-proportional setpoints, namely time-dependent radiation values, are determined from a specific, ideal alloy during melting. This results in a target curve representing a comparison diagram 10 educated. After the target curve 10 Once the alloy in question has been determined, it serves as a comparison curve for all alloys to be tested, that of the alloy of the target curve 10 should correspond. The time-dependent infrared radiation values determined on the basis of the alloy in each case are used to form a measurement curve 11 used. In the 1 are both the target curve 10 as well as the measurement curve 11 shown. The latter deviates from the target curve 10 from. There can be several reasons for this: The main reason is that the target curve 10 has been recorded with a different amount of material than the measurement curve 11 , Another reason is that the distance of the measuring sensor from the surface of the material to be measured is larger or smaller than in the target curve 10 , To that of the target curve 10 deviating measurement curve 11 for testing purposes with the target curve 10 To be able to compare, the measurement curve is normalized according to the invention 11 ,

The normalization of the measurement curve 11 takes place with the help of a characteristic single point. A solidus point is preferably used for this 12 used. The solidus point 12 is where the solid casting material begins to become liquid. For the liquefaction of the solid material, an energy of change in the state of matter is required, which leads to the temperature and thus the radiation energy of the casting material not changing or changing only insignificantly over a certain point in time. The solidus point is characterized 12 both in the target curve 10 as well as in the measurement curve 11 by a slope of the curve that is close to 0. In solidus point 12 So the curve runs almost horizontally. The solidus point can be drawn 12 determine by a tangent slightly inclined to the horizontal 13 with which an intersection of the target curve 10 or the measurement curve 11 is formed. Where the parallel tangents 13 the target curve 10 on the one hand and the measurement curve 11 on the other hand, the respective solidus point is located 12 ( 1 ). The solidus point can be calculated 12 determine the difference between two radiation values in succession in a specific, short time interval. If this difference decreases to a certain predetermined difference value, this is the solidus point we are looking for 12 , In addition to forming differences, the solidus point 12 can also be calculated by means of a differential, namely by deriving the radiation over time.

For normalizing the measurement curve 11 first the radiation values and the time values at the solidus point 12 the target curve 10 to the corresponding values at the solidus point 12 the measurement curve 11 in relation, according to the following equations: I 10 : I 11 = F I t 10 : t 11 = F t

With these factors (F _I ; F _t ) they become the solidus point 12 lying emission and time values of the measurement curve 11 multiplied to the normalized solidus point, which is the solidus point 12 the target curve 10 equivalent. The following calculations are carried out: I 11 × F I = I 14 t 11 × F t = t 14

The remaining time-dependent and temperature-proportional radiation values of the measurement curve 11 are multiplied by the same factors F _I and F _t . The resulting standardized values lead to the standardized measurement curve 14 , This is in the 2 and 3 shown in dashed lines. In the 2 it is clearly recognizable that the solidus point 12 the target curve 10 with the solidus point 12 the standardized measurement curve 14 coincides.

The normalized measurement curve 14 forms a test curve with the target curve representing the comparison curve 10 is comparable. When visually comparing the target curve 10 with the standardized measurement curve 14 the two curves are superimposed. This can be done by placing the target curve on a transparent template sheet 10 is plotted in a coordinate system. A comparison with the standardized measurement curve 14 takes place in such a way that on the standardized measurement curve 14 the transparent sheet with the target curve 10 is applied as a template for overlapping coordinate systems. The two curves of that in the 2 drawn target curve 10 and the standardized measurement curve 14 , As far as the deviations as in the 2 shown example are only very small, it can be assumed that those with the normalized measurement curve 14 tested alloy essentially corresponds to the desired alloy.

In the 3 finds a comparison chart 15 Use that consists of two limit curves 16 and 17 composed. The limit curves 16 and 17 are formed from the target curve 10 by the upper limit curve 16 the maximum values and the lower limit curve 17 indicates the minimum values. Im from the limit curves 16 and 17 enclosed (stripe-shaped) area, which increases slightly towards increasing radiation or time values, i.e. widens, the standardized measurement curve 14 if the alloy to be tested is OK. One such example is in the 3 shown where the normalized trace 14 the area between the limit curves 16 and 17 does not leave.

The measured values obtained during the testing of the alloy to be melted, namely infrared emission values recorded at regular time intervals, are expediently entered into a computer which carries out the normalization, that is to say the conversion of each measured value with the factors F _I and F _t . The computer thus determines the individual points of the standardized measurement curve 14 , These points are called the normalized trace 14 output by, for example, a printer connected to the melting device or a casting device. This creates a measurement protocol, the standardized measurement curve 14 with a target curve recorded on a template 10 or limit curves recorded on a template 16 and 17 is compared visually. Alternatively, it is also conceivable to use the printer with the standardized measurement curve 14 equal to the target curve 10 or the limit curves 16 and 17 print. Then an immediate evaluation is possible without the use of a template, at any time. This permanently documents the test result.

Alternatively, it is also possible to display the target curve on a computer screen 10 or the limit curves 16 . 17 and the normalized measurement curve 14 display. The standardized measurement curve 14 completed with progressive heating of the casting alloy, and if necessary the melting process can be terminated prematurely if it emerges that the standardized measurement curve 14 beyond the permitted range from the target curve 10 differs.

The The method described above is limited to the exam based on the time-related radiation energy of the casting material perform. It can other temperature-proportional values or actual values Temperature values are used.

10

Ideal Trend

11

measured curve

12

solidus

13

tangent

14

normalized measured curve

15

comparison chart

16

limit curve (upper)

17

limit curve (lower)

Claims (8)

Method for testing dental casting materials, wherein time-dependent temperature values or temperature-related values of the dental casting material are measured during the melting of the dental casting material, which a measurement curve ( 11 ) and, based on the measured time values and temperature values or temperature-related values, the solidus point ( 12 ) is determined and the temperature value ( I ₁₀ ) or the temperature-related value (I ₁₀ ) and the time value (t ₁₀ ) at the solidus point ( 12 ) a target curve ( 10 ) to the temperature value (I ₁₁ ) or the temperature-related value (I ₁₁ ) and the time value (t ₁₁ ) at the solidus point ( 12 ) of the measurement curve ( 11 ) in relation to the formation of two ratio factors and the measured time values and temperature values or temperature-related values are multiplied by the respective ratio factor, whereby a standardized measurement curve ( 14 ) arises with the target curve ( 10 ) is compared. Method according to claim 1, characterized in that the standardized measurement curve ( 14 ) with the target curve ( 10 ) is compared in such a way that it is checked whether the time values and temperature values or temperature-related values of the standardized measurement curve ( 14 ) the respective time value and temperature value or temperature-related value of the target curve ( 10 ) more than a certain value. Method according to one of claims 1 to 2, characterized in that a target curve ( 10 ) a specific alloy of the dental casting material is used. Method according to one of claims 1 to 3, characterized in that the standardized measurement curve ( 14 ) of a dental casting material to be tested with the target curve ( 10 ) a dental casting material of the same or comparable alloy is checked. Method according to one of claims 1 to 4, characterized in that the standardized measurement curve ( 14 ) and / or the target curve ( 10 ) can be printed out by a printer assigned to the melting or casting device used for melting the dental casting material. Method according to one of claims 1 to 5, characterized in that a comparison diagram ( 15 ) is used, which has an upper and a lower limit curve ( 16 . 17 ), on the basis of which it is checked whether the standardized measurement curve ( 14 ) in the of the limit curves ( 16 . 17 ) enclosed area. Method according to one of claims 1 to 6, characterized in that that the temperature-related values are radiation values of the dental casting material are determined with an IR radiation measuring device. Method according to one of claims 1 to 7, characterized in that as a standardized measurement curve ( 14 ) a standardized IR emission curve is used.